Abstract
Plants have species specific wide varieties of flower color by combining anthocyanin structures, oexisting compounds, vacuolar pH and metal ions. A plant species can accumulate limited kinds of anthocyanins due to its genetic constrain. Rose, carnation and chrysanthemum lack violet/blue colour due to the lack of delphinidin and gentian and iris lack blight red due to the lack of pelargonidin.
The number of hydroxyl group on the B-ring greatly affects the color and is regulated by flavonoid 3'-hydroxylase and flavonoid 3',5'-hydroxylase. Their heterologous expression and/or suppression of their endogenous expression can confer a new pathway leading to anthocyanins that the target spices does not accumulate by nature. Careful selection of a host cultivar, coexpression of dihydroflavonol 4-reductase having proper substrate specificity and/or down regulation of a competing pathway is also necessary.
Transgenic rose and carnation accumulating delphinidin and wearing blue hue have been commercialized. Intense red petunia and tobacco have been also made. Regulation of anthocyanin modification, vacuolar pH and metal ion uptake would pave a way to generate more colorful flower.
